The Code

Here is the resulting script:

#!/bin/sh
# /usr/local/etc/rc.d/wi0
# Configure wireless interface

# See the ifconfig(8), dhclient(8) and route(8) man pages for further 
# assistance.

NIC=wi0

case $1 in 
dhome)
       ifconfig ${NIC} ssid "myhome" authmode "shared" nwkey 0x123456789a
       dhclient ${NIC}
       echo ${NIC}
       ;;
shome)
       ifconfig ${NIC} inet 192.168.1.21 ssid "myhome" authmode "shared" 
       nwkey 0x123456789a netmask 255.255.255.0
       route add default 192.168.1.1
       echo nameserver 24.204.0.4 > /etc/resolv.conf
       echo nameserver 24.204.0.5 >> /etc/resolv.conf
       echo ${NIC}
       ;;
dsister)
       ifconfig ${NIC} ssid "sisterhome" authmode "shared" nwkey \
           0x987654321a
       dhclient ${NIC}
       echo ${NIC}
       ;;
stop)
       [ -s /var/run/dhclient.pid ] && kill `cat /var/run/dhclient.pid` \ 
           && rm /var/run/dhclient.pid
       ifconfig ${NIC} remove
       echo " ${NIC} removed"
       ;;
status)
       ifconfig ${NIC}
       ;;
*)
       echo "usage: /usr/local/etc/${NIC} [dhome|shome|dsister|stop|status]"
       ;;
esac

Note that the stop option kills dhclient. If you will be using multiple network interfaces, you may wish to delete the line that reads:

[ -s /var/run/dhclient.pid ] && kill `cat /var/run/dhclient.pid` && rm \
      /var/run/dhclient.pid

The script should be owned by root and be readable by root only. If you create your script as a normal user, you need to change its owner. Become the superuser, and:

# chown root:wheel /usr/local/etc/rc.d/wi0
# chmod 700 /usr/local/etc/wi0